Proce



Patented Apr. 24, 1945 Francis E; Gislak lndi napolisrand Qrinn- Quivr y ham. Speedway City, Ind-,assiznms Reilly Tar &, Chemical Corporation Indian apolis,.1nd.,, a corporation of, Indiana NoDranrihg. ApDlicationneccmber 20 19M,

Serial No. r

14 Claims. (or. 260 -1290) I Quit invention relates to the separation of 3-picoline, 4-picoline, and 2,6-lutidine from one another.

These three compounds, fl-picoline, -picoline, and ZaG-Iutidineare commonly associated with i one another as ordinarily prepared from coal tar. But they are diffioultto separate one from another, because their properties are closely alike; especially their boiling: points, so, that separating them by fractional distillation very diffieultl All three of these compounds boil at very nearly the same temperature-about Lad-145- We have found, contrary to what might be expected, that the hydrohalides: oi 3--picoline, -picolinepand 2;,6-1utidine are distillable; that if in a mixture of two or all three of these compounds we convert them into their respective hydrohalides, we obtain a fairly wide separation oi boiling; points; and that the resultant mixture of these hydrohalides is readily separable by fractional distillation on account of; that relatively: large difference in boiling points. After that separation; the separated hydrohalides may if desired be separately reconverted in any suit able manner into the bases irom which they were derived, as by treatmentwith an alkali-metal hydroxide or ammonia.

The relatively wide difierence in the boiling points of the hydrohalides is exemplified by the hydrochlorides, the most convenient. ones to. use. These are about as follows:

The boiling (points of the several hydrofluorides, the several hydrobromides, and the several hydriodides differ among themselves in much the same manner; and in each case materially more widely than do the boiling points of the three bases.

We can use our process of separation to separate mixtures of any two of the three bases, as well as mixtures of all three. In each instance, the mixture, whether of two of three components, i treated with a hydrogen halide, to convert the bases in the mixture into their hydrohalides; then the mixture of hydrohalides is subjected to fractional distillation, to separate the component hydrohalides by reason of their differences in boiling point; and then, if desired, any or all of the the bases from which. they came). any suitabl manner 1 y y t The equipment, and more especially the t l and the iraotione ing. column ho ld e r sis anttothe. attack at the hydroha ides. r i r in convertin athe mixture of b se into the hydrohalides, we may use: either aqueous solutions of the desir dv hydr genhalide, or the hydrogen halides themselves. instance it we convert the basesinto hydr eh-lorides, whi h. re the hydr halides we ureter for conven ence W may treat the mixture or bases with aqufiwi W- droehlorio: aoi-d or may bubble gaseous; hydrogen chloride through suchqmixture. y s The iollowing; ar xampl s of our process:

Elwample l.,Ninety thr e grams l mole). oia or mixture containing approximately of 3'- piooline and 55%, of. 4spicolm i reacted with 36. ea t1..mo1e), of. hydrog n chloride; to produce a mixture of the hydrochlorides of B-picoline and 4-picoline'. This mixtureof hydrochlorides is subjected to fractional, distillation; through an efficient iractionating column, o o t in first h p oo1ine hydrochloride boilin a abo t 33 C- and later the. i picoline hydrochl ride boil n a about 240? C. These separated hydroch orid or either of them may be separately treated to reconstitute the respective bases, li-Pi Qlih B a spice-line, in any onvenient mann r most com veniently by treatment with caustic. soda. If caustic soda is used, it is d sirably fairly concentrat d say about% or mor Th freed separated pipelines thus obtained are usually Of a purity of 0% orbetter for both 3 picoline and d-picoline.

Example 2.Examp1e 1 is repeated, save that instead of using a mole of hydrogen chloride we use a mole of hydrogen bromide. Specifically, 93 gram (1 mole) of a mixture containing approximately 62% of 3-pico1ine and 38% of d-picoline is reacted with 81 grams (1 mo1e) of hydrogen bromide. The resultant mixture of hydrobromides is subjected to fractional distillation through an efiicient fractionating column, to obtain first the 3-picoline hydrobromide, which boils at about 329 C., and then the 4-picoline hydrobromide, which boils at about 335 C. The

two separated picoline hydrobromides may be separately treated to reconstitute the respective bases, as by treatment with caustic soda as in Example 1. The 3-pico1ine thus obtained is of about 94 to 96% purity; and the 4-picoline thus obtained is of over 90% purity. n

Example 3.The procedures of Examples 1 and separated hydrohalides may be reconverted into 2 are repeated, save that hydrogen iodide is used Example 5.--About 97.4 g.. (about 1 mole of total base) of a mixture containing approximately 39% f 3-picoline, 38% of 2,6-lutidine, and 23% of 4-picoline, is reacted with about 95 g. of concentrated aqueous hydrochloric acid (about 37-38%)about 1 mole in terms-of the acid itself. This converts all three bases into their hydrochlorides. The water is separated from the mixture of hydrochlorides, as by distillation or evaporation; and then the remainingmixture of hydrochlorides is separated into its component hydrochlorides through an efiicient fractionating column. over first, then the 4-picoline hydrochloride, and finally the 2,6-lutidine hydrochloride, by reason of their successively higher boiling points in the order named. The three separated hydrochlorides may then if desired be reconverted into the bases from which they were derived, as by treatment with caustic soda or ammonia or other strong base. The B-picoline thus obtained is ordinarily of about 95% purity, the i-picoline of about 90% purity, and the 2,6-lutidine of between 80 and 90% purity.

In the foregoing examples We have contemplated usinga fractionating column of rather high efficiency. But the difference in boiling points among the different hydrohalides of 3- picoline, e-picoline, and 2,6-lutidine is sufficient that high efficiency in a fractionating column is not essential if high purities of the separated components is not important. Indeed, the differences in boiling points are such that fair separataining two or more of the bases 3-picoline, 4-

picoline, and 2,6-lutidine, which consists in converting the bases in the mixture into their hydrohalides, separating the hydrohalides by fractional distillation, and reconverting the separated hydrohalides into the respective bases from which they were derived. m

The 3-picoline hydrochloride passes 3. In the process of obtaining the separate components of a mixture containing two or more of the bases 3-picoline, 4-picoline, and 2,6-lutidine, the step of fractionally distilling a mixture of the hydrohalides of said bases.

4. The process as set forth in claim 1 in which the hydrohalides into which the bases are converted are hydrochlorides.

5. The process as set forth in claim 2, in which the hydrohalides into which the bases are converted are hydrochlorides.

9. The process step as set forth in claim 3, in.

which the hydrohalides which are distilled are hydrobromides.

10. The process as set forth in claim 1, in which the hydrohalides into which the bases are converted are hydrofiuorides.

11. The process as set forth in claim 2, in which the hydrohalides into which the bases are converted are hydrofiuorides.

12. The process step as set forth in claim 3, in which the hydrohalides which are distilled are hydrofluorides.

13. In a process of separating 3-picoline from a mixture consisting essentially of this base and at least one'of the bases 4-picoline and 2,6-lutidine, the step which comprises forming hydrochlorides of the bases in the mixture, and fractionally distilling the hydrochlorides to separate a distillate fraction enriched in 3-picoline hydrochloride.

14. The process for the production of 3-picoline from a mixture of coal-tar bases consisting es-' sentiall'y of 3-pico1ine and at least one of the bases 4-pico1ine and 2,6-1utidine, which comprises separating such a mixture from coal tar by fractional distillation, treating this mixture with sufficient hydrochloric acid to convert all these bases to their hydrochlorides, subjecting the resulting mixture of hydrochlorides to fractional distillation to separate out a distillate enriched in 3-picoline hydrochloride, and treating the 3- picoline hydrochloride thus obtained with alkali to obtain 3-picoline.

FRANCIS E. CISLAK. ORIN D. CUNNINGHAM. 

